[time-nuts] quartz thermometers

Neville Michie namichie at gmail.com
Sat Mar 12 05:19:12 EST 2016


It always puzzled me that quartz crystals would be considered prime temperature sensors.
I can see that an instrument could be built that reliably showed many decimal places of reading,
but I could never accept that a vacuum mounted quartz crystal would be closely enough 
thermally coupled to whatever was having its temperature measured.
Sensors like thermistors, thermocouples and platinum resistors can be made of the right shape and size to 
thermally couple to solids and liquids and so can make successful measurement systems.
Many important measurements rely on having no disturbance of the physical system by the 
use of the thermometer.

cheers,
Neville Michie


> On 12 Mar 2016, at 8:21 pm, ken hartman <ken at hartmans.org> wrote:
> 
> Interestingly, the use of AC-cut crystals (high linear tempco of frequency)
> is found in the development of OCXOs. Using a reference AC-cut resonator -
> in place of the final AT/SC resonator - one can learn much about the
> thermal  characteristics of the oven loop performance. While not a precise
> temp sensor, it is a high sensitivity  indicator of  temperature variations
> of the resonator.
> 
> On Fri, Mar 11, 2016 at 11:44 PM, Bill Hawkins <bill.iaxs at pobox.com> wrote:
> 
>> It may be that the need for that kind of resolution died out.
>> 
>> The next step up from quartz thermometry is resistance thermometry.
>> The linearization equation for platinum has enough terms to make it
>> uncertain around .01 C.
>> Temperature calibration baths usually use platinum resistance sensors.
>> 
>> It may be that the triple point of water does not have the certainty to
>> reach '0.0001C'
>> 
>> Disclaimer: I only worked with industrial sensors from Rosemount, Inc.
>> as an employee.
>> 
>> Bill Hawkins
>> 
>> 
>> -----Original Message-----
>> From: Alan Ambrose
>> Sent: Friday, March 11, 2016 11:42 AM
>> 
>> Hi,
>> 
>> I hope this is still relevant and not too off-topic...but since it
>> involves crystals and tempco...
>> 
>> Quartz thermometers (e.g. the HP 2804A) with their 'linear cut' crystals
>> and '0.0001C resolution' seem to have been a thing from the mid-60's to
>> the mid-80's:
>> 
>> http://www.hparchive.com/Journals/HPJ-1965-03.pdf
>> 
>> There still appear to be some manufacturers making the crystals:
>> 
>> http://www.statek.com/products/pdf/Temp%20Sensor%2010162%20Rev%20B.pdf
>> 
>> Anyone know why they died out? Did a better technology replace them?
>> 
>> TIA, Alan
>> 
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